Berlin 2005 – wissenschaftliches Programm

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DS: Dünne Schichten

DS 23: Postersitzung I

DS 23.22: Poster

Freitag, 4. März 2005, 16:00–18:30, Poster TU B

Comparison of low temperature nitrided austenitic and martensitic stainless steel — •Darina Manova, Stephan Mändl, Horst Neumann, and Bernd Rauschenbach — Leibniz-Institut für Oberflächenmodifizierung, Leipzig, Germany

Nitriding of austenitic stainless steels with energetic ions between 1 and 50 keV at temperatures between 350 and 380 ^∘C is a common process to obtain hard and wear resistant surface layers while retaining the corrosion resistance. In this temperature range, no CrN precipitates are formed, yet a fast nitrogen diffusion leads to a layer thickness of 1 - 10 µm within 1 hour. Furthermore, an anisotropic expansion of the austenitic lattice by 5 - 10% is observed.

Recent experiments show that a similar effect is observed in martensitic stainless steel, where the same process conditions result in an expanded martensite structure. The relative hardness increase of a factor of 3 - 4 is similar for both materials, thus the martensitic steels with an initial higher hardness retain its advantage after the nitrogen implantation. However, the nitrogen insertion leads to the same absolute wear resistance, i.e. the wear rate is decreased by 3 - 5 orders of magnitude for austenites and 1 - 2 orders of magnitude for martensites. It is argued that the build-up of compressive stress during the high-dose ion implantation may be responsible for the outstanding hardness properties of expanded austenite and expanded martensite, while the wear is independently determined by the nitrogen in solid solution.

This work was supported by EU/SMWA project 6204/947.